Reciprocating compressor

ABSTRACT

A reciprocating compressor, comprising a cylinder block ( 1 ) having a cylinder bore ( 12 ) formed therein, a rear head ( 3 ) fixed to the cylinder block through a valve plate ( 2 ) and having a suction chamber ( 26 ) and a discharge chamber ( 27 ) formed therein, a front head ( 4 ) fixed to the cylinder block ( 1 ) and having a crankcase ( 6 ) formed therein, pistons ( 13 ) reciprocatingly sliding in the cylinder bore according to the rotation of a shaft ( 7 ) installed so as to pass through the crankcase ( 6 ), a means for separating lubricating oil mixed in working fluid discharged into the discharge chamber ( 27 ), and an oil tank ( 30 ) for storing the lubricating oil separated by the oil separation means, wherein the lubricating oil stored in the oil tank ( 30 ) is cooled by working fluid sucked from the outside and led into the suction chamber ( 26 ), whereby the durability of sliding portions can be increased by effectively cooling the lubricating oil in the compressor to assure excellent lubrication at the sliding portions.

This application is a U.S. National Phase Application under 35 USC 371of International Application PCT/JP02/13788 filed Dec. 27, 2002.

TECHNICAL FIELD

The present invention relates to a reciprocating compressor ideal in anapplication in a supercritical freezing cycle in which a coolant such asCO₂ (carbon dioxide) is used as a working fluid, and more specifically,it relates to a reciprocating compressor adopting a structure that makesit possible to separate lubricating oil mixed in the compressed workingfluid and keep the separated lubricating oil within the compressor.

BACKGROUND ART

The pressure in a supercritical freezing cycle in which CO₂ (carbondioxide) is used as the coolant rises to a level approximately 10 timesas high as the pressure in a freezing cycle in which a Freon coolant isused. For this reason, as the coolant is compressed inside a cylinderbore, the temperature of the discharged coolant, too, increases due tothe raised discharge pressure, and since this lowers the viscosity ofthe lubricating oil, the lubrication at sliding portions becomes poor,which leads to a problem of poor durability of the sliding portions.Further problems may arise if the lubricating oil becomes degraded dueto the heat or if the lowered viscosity causes sliding portions toseize.

This issue is addressed in the related art with a structure disclosed inJapanese Unexamined Patent Publication No. 2000-18154, in whichdegradation of the lubricating oil and the occurrence of a seize areprevented by forming a continuous hollow portion around a plurality ofcylinder bores formed at a cylinder block, supplying a feedback coolant(a cooling medium), which is taken in via a suction port, into thehollow portion and preventing the temperature inside the bores fromrising to an excessive extent during the compression phase throughactive heat exchange of the heat inside the individual cylinder boresand the feedback coolant.

However, while the structure described above is advantageous in that thecylinder bores are cooled to a sufficient degree, it simply cools downthe lubricating oil by cooling the cylinder bores. Thus, when thelubricating oil mixed in the discharged coolant is separated and isdirectly returned to the crankcase, the temperature of the returninglubricating oil will be high. As a result, good lubrication will not beachieved in the crankcase due to the presence of a significant quantityof lubricating oil with lowered viscosity, which gives rise to a concernfor lowered durability of the sliding portions. In addition, there is aconcern in that the cylinder bores with the hollow portion formed aroundthem in the structure described above may become deformed readily as thedescending loads of the pistons are applied.

Accordingly, a main object of the present invention is to provide areciprocating compressor that achieves improved durability in thesliding portions by effectively cooling the lubricating oil inside thecompressor and assuring good lubrication at the sliding portions.Further objects of the present invention are to assure effective coolingof the cylinder bores and the pistons and to prevent deformation of thebores, which tends to occur readily when a hollow portion is formedaround the cylinder bores.

DISCLOSURE OF THE INVENTION

In order to achieve the objects described above, the reciprocatingcompressor according to the present invention comprising a cylinderblock having a plurality of cylinder bores formed therein, a valve platehaving formed therein pairs of holes, each pair constituted of a suctionhole and a discharge hole in correspondence to one of the cylinderbores, a first head fixed to the cylinder block via the valve plate andhaving formed therein a suction chamber that is allowed to communicatewith the suction holes and a discharge chamber that is allowed tocommunicate with the discharge holes, a second head fixed to thecylinder block and having formed therein a crankcase, a shaft rotatablypassing through the crankcase and pistons that slide back and forthinside the cylinder bores as the shaft rotates, is characterized in thatan oil separation means that separates lubricating oil mixed in aworking fluid discharged to the discharge chamber and an oil tank atwhich the lubricating oil having been separated by the oil separationmeans is collected are provided and that the lubricating oil collectedat the oil tank is cooled with a working fluid taken in from the outsideand guided into the suction chamber.

Since the lubricating oil having been separated from the discharge gasby the oil separation means is collected in the oil tank and is thencooled with the uncompressed, relatively cool working fluid which istaken in from the outside and is guided into the suction chamber, theviscosity of the lubricating oil collected in the oil tank can besustained at a high level to assure better lubrication.

It is desirable that part of the oil tank is disposed at the cylinderblock and that a suction path through which the working fluid flows isformed at the cylinder block so as to surround the oil tank.

By adopting the structure described above, it becomes possible to coolthe oil tank with a high degree of efficiency as the working fluidguided into the suction chamber is caused to flow around the oil tankwhile it flows through the suction path at the cylinder block.

More specifically, the suction path should include a suction portthrough which the working fluid is taken in from the outside, a chamberformed to surround the oil tank at the cylinder block and open towardthe valve plate, a first passage which communicates between the suctionport and the chamber and a second passage formed at the valve plate soas to communicate between the chamber and the suction chamber.

Alternatively, part of the oil tank may be disposed at the first headwith the suction chamber formed so as to surround the oil tank at thefirst head. In addition, the oil separation means may include an oilseparation chamber communicating with the discharge chamber, mayseparate the lubricating oil centrifugally in the oil separation chamberby rotating the working fluid flowing in from the discharge chamber andmay allow the oil separation chamber to partially overlap the oil tankso as to achieve communication.

It is to be noted that the chamber in the structure described above maybe formed so as to surround the cylinder bores as well. In such a case,it is possible to cool the inside of the cylinder bores.

Furthermore, if the suction path is formed by retaining tubular wallsaround the oil tank and the cylinder bores, it is desirable to bridgethe tubular walls with reinforcement ribs in order to preventdeformation of the cylinder bores, which would otherwise be caused bythe descending loads of the pistons.

Based upon the structure described above through which the lubricatingoil is actively cooled, the lubricating oil may be supplied through twosupply path systems so as to supply the lubricating oil to portions thatneed to be lubricated with a high degree of efficiency. Namely, acontrol passage, the degree of openness of which is adjusted with apressure control valve, may be formed between the discharge chamber andthe crankcase, a first lubricating oil supply path which opens up an endof the control passage facing the crankcase toward a peripheral edge ofa swashplate and a second lubricating oil supply path through which thelubricating oil having been collected in the oil tank is supplied tolubrication-requiring portions around the shaft via a passage formed atthe shaft may be provided, and the crankcase and the chamber may be madeto communicate with each other via a leak passage formed at the cylinderblock.

In the structure described above, the working fluid containing thelubricating oil, which is discharged into the discharge chamber, isdirectly supplied toward the peripheral edge of the swashplate connectedto the pistons via the first lubricating oil supply path. In addition,the lubricating oil having been separated from the working fluid andcollected at the oil tank is directly supplied to thelubrication-requiring portions around the shaft, e.g., a shaft sealmember sealing the area between the second head and the shaft. Thus, thelubricating oil is supplied to various lubrication-requiring portionsvia the appropriate lubricating oil supply paths.

Alternatively, a control passage, the degree of openness of which isadjusted with a pressure control valve, may be formed between thedischarge chamber and the crankcase, a first lubricating oil supply pathwhich opens up an end of the control passage facing the crankcase towarda peripheral edge of a swashplate and a second lubricating oil supplypath through which the lubricating oil having been collected in the oiltank is supplied to lubrication-requiring portions around the shaft viaa passage formed at the cylinder block and the second head and a passageformed at the shaft communicating with the passage and the crankcase andthe chamber at the cylinder block and the second head may be provided,may be made to communicate with each other via the passage formed at theshaft and a leak passage formed at the cylinder block which communicateswith the passage at the shaft.

In this structure, too, the working fluid containing the lubricatingoil, which is discharged into the discharge chamber, is directlysupplied toward the peripheral edge of the swashplate connected to thepistons via the first lubricating oil supply path. In addition, thelubricating oil having been separated from the working fluid andcollected at the oil tank is directly supplied to thelubrication-requiring portions around the shaft, e.g., a shaft sealmember sealing the area between the second head and the shaft. Thus, thelubricating oil can be supplied to various lubrication-requiringportions via the appropriate lubricating oil supply paths.

It is to be noted that if tightening bolts are used to fasten thecylinder block, the valve plate, the first head and the second headtogether as an integrated unit, the tightening bolts should be disposedfurther outside relative to the cylinder bores at positions with thesame phase as that of the cylinder bores so as to ensure that there isno obstacle in the suction path. In addition, it is desirable to assurea high level of pressure withstanding performance and a high level ofairtightness by disposing a greater number of tightening bolts than thenumber of cylinder bores. Moreover, a sub-suction chamber where theworking fluid flowing in from the suction port is stored may be formedbetween the suction port and the chamber in order to reduce the extentof suction pulsation.

While the structure described above is ideal in an application in astandard compressor in the related art, i.e., a compressor having thefirst head constituting a rear head and the second head constituting afront head, it may also be adopted in a compressor having the first headconstituting a front head and the second head constituting a rear head.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a reciprocating compressor according tothe present invention, taken along line I-I in FIG. 2;

FIG. 2(a) shows an end surface of the cylinder block of the compressorshown in FIG. 1, viewed from the rear head side, and FIG. 2(b) shows anend surface of the valve plate in the compressor shown in FIG. 1;

FIG. 3 is an enlarged view of the discharge chamber, provided tofacilitate an explanation of the relationship between the stopper 60formed as an integrated part of the rear head 3 and the discharge valve29;

FIG. 4 shows another structural example that may be adopted tocommunicate between the oil separation chamber 33 and the oil tank 30;

FIG. 5 is a sectional view of a reciprocating compressor according tothe present invention, adopting different structures in the lubricatingoil supply paths through which the lubricating oil is supplied from theoil tank and in the path through which the crankcase and the chambercommunicate;

FIG. 6 shows part of the end surface of the cylinder block provided tofacilitate an explanation of an example in which tightening bolts aredisposed at different fastening positions;

FIG. 7 illustrates a structure having sub-suction chambers disposed inthe passage that communicates between the suction port and the chamber;and

FIG. 8 shows another structure having sub-suctions chamber in a passagethat communicates between the suction port and the chamber with FIG.8(b) showing a sectional view taken along line II-II in FIG. 8(a).

BEST MODE FOR CARRYING OUT THE INVENTION

The following is an explanation of embodiments of the present invention,given in reference to the drawings. The reciprocating compressor inFIGS. 1 and 2, which is employed in a supercritical freezing cycle thatuses a coolant such as CO₂ (carbon dioxide) or the like as a workingfluid, comprises a cylinder block 1, a rear head 3 mounted on the rearside (the right side in the figures) of the cylinder block 1 via a valveplate 2 and a front head 4 mounted so as to close off the front side(the left side in the figures) of the cylinder block 1. The front head4, the cylinder block 1, the valve plate 2 and the rear head 3 arefastened together along the axial direction with tightening bolts 5thereby constituting a housing for the entire compressor.

In a crankcase 6 formed by mounting the front head 4 at the cylinderblock 1, a shaft 7 with one end thereof projecting out from the fronthead 4 to be fixed to the armature of an electromagnetic clutch (notshown) is housed. The shaft 7 is rotatably supported on the same endside via a thrust flange 15 by a radial bearing 16 and a thrust bearing17 housed in the front head 4, whereas the other end of the shaft 7 isrotatably supported by a radial bearing 9 and a thrust bearing 10 housedin the cylinder block 1.

At the cylinder block 1, a bearing housing chamber 11 in which theradial bearing 9 and the thrust bearing 10 are housed and a plurality(6) of cylinder bores 12 disposed over equal intervals in a circlearound the shaft so as to surround the shaft 7 are formed. Inside eachcylinder bore 12, a single-ended piston is inserted so as to slidereciprocally. It is to be noted that in this example, the tighteningbolts 5 are each provided further outward relative to a cylinder bore ata position with the same phase as that of the cylinder bore 12, i.e., onan extension of a straight line that connects the shaft 7 and thecylinder bore 12.

The thrust flange 15 that rotates together with the shaft 7 is fixed tothe shaft 7 in the crankcase. The thrust flange 15 is disposed so as toform a shaft seal chamber 18 where the shaft seal device constitutedwith a mechanical seal 8 is housed between the front head 4 and thethrust flange 15 on its front end side supported with the radial bearing16.

In addition, a swashplate 20 is connected to the thrust flange 15 via alink mechanism 19. The swashplate 20 supported so as to be allowed totilt around a hinge ball 21 which is fitted at the shaft 7 with play,rotates as one with the thrust flange 15 in synchronization with therotation of the thrust flange 15. The swashplate is held at the tailportions of single-ended pistons 13 projecting out into the crankcase 6via a pair of shoes 22 disposed so as to enclose the peripheral edge ofthe swashplate 20 from the front and the rear. Thus, as the shaft 7rotates causing the swashplate 20, too, to rotate, the rotating motionof the swashplate 20 is converted to a reciprocal linear motion of eachsingle-ended piston 13 via the shoes 22, and the reciprocal motion ofthe single-ended pistons 13 alters the volumetric capacity of acompression space 23 formed inside the cylinder bore 12 between thesingle-ended piston 13 and the valve plate 2.

Pairs of holes each constituted of a suction hole 24 and a dischargehole 25 are formed in the valve plate 2 in correspondence to theindividual cylinder bores 12, and a suction chamber 26 where the workingfluid to be supplied to the compression spaces 23 is stored and adischarge chamber 27 where the working fluid discharged from thecompression spaces 23 is collected are formed at the rear head 3. Thesuction chamber 26, which is formed continuously around the dischargechamber 27, communicates with the compression spaces 23 via the suctionholes 24 at the valve plate 2, whereas the discharge chamber 27, whichis formed continuously around and oil tank 30 detailed below,communicates with the compression spaces 23 via the discharge holes 25at the valve plate 2. In addition, the suction holes 24 are eachopened/closed with a suction valve 28 disposed at the end surface of thevalve plate 2 on the front side, and the discharge holes 25 are eachopened/closed with a discharge valve 29 disposed at the end surface ofthe valve plate 2 on the rear side. As shown in FIG. 3, a stopper 60formed as an integrated part of the rear head 3 regulates the liftquantity of the discharge valve 29 when it is opened, and in thisexample in particular, the durability of the discharge valve 29 isassured by forming the surface of the stopper 60 facing opposite thedischarge valve 29 so that the distance from the discharge hole 25lengthens gradually as it ranges toward the free end of the dischargevalve 29 and thus by allowing the discharge valve 29 and the stopper 60to achieve surface content.

A control passage 31 communicating between the bottom portion of thedischarge chamber 27 and the crankcase 6 is formed at the cylinder block1, the valve plate 2 and the rear head 3, and a pressure control valve62 with which the degree of openness of the control passage 31 isadjusted is disposed at the rear head 3. The pressure control valve 62is used to control the crankcase pressure by adjusting the state ofcommunication between the discharge chamber 27 and the crankcase 6 so asto set the suction chamber pressure to a desired level. With thepressure control valve 62, the difference between the crankcase pressureand the pressure inside the cylinder bores applied to the front and therear of the single-ended pistons 13 is adjusted, thereby also adjustingthe tilt angle of the swashplate 20 to enable control of the stroke ofthe single-ended pistons 13, i.e., the discharge capacity. In addition,the end of the control passage 31 facing the crankcase 6 is formed so asto open toward the peripheral edge of the swashplate 20 that slidablycontacts the shoes 22, and the control passage 31 forms a firstlubricating oil supply path.

An oil separation means that separates the lubricating oil mixed in theworking fluid discharged into the discharge chamber 27 throughcentrifugal separation is provided at the rear head 3. The oilseparation means includes an oil separation chamber 33 that communicateswith the upper portion of the discharge chamber 27 via a communicatingpassage 32 in the rear head 3. The oil separation chamber 33 is a spaceformed to range along the vertical direction, and inside the oilseparation chamber 33, a gas guiding tube 34 is disposed so as todescend from the top. As the working fluid guided into the oilseparation chamber 33 via the communicating passage 32 is guideddownward while rotating around the gas guiding tube 34, the lubricatingoil mixed in the working fluid becomes separated. Then, the workingfluid from which the lubricating oil has been separated flows outthrough a discharge port (not shown) via the gas guiding tube 34,whereas the lubricating oil having become separated is collected intothe oil tank 30 located below the oil separation chamber 33 via an oiloutlet hole 35 formed at the bottom of the oil separation chamber 33.Reference 36 indicates a dust removing filter disposed inside the oiltank 30.

It is to be noted that while the oil separation chamber 33 is locatedabove the oil tank 30 and the oil separation chamber 33 and the oil tank30 are made to communicate with each other via the oil outlet hole 35 inthe example, the oil separation chamber 33 may instead be formed so asto partially overlap with the oil tank as shown in FIG. 4 with the oilseparation chamber 33 and the oil tank 30 achieving communication witheach other through an opening 61 formed with a portion of the internalperipheral surface of the oil separation chamber 33 made to open intothe oil tank 30. More specifically, it is desirable to allow the lowerend of the oil separation chamber 33 to partially overlap the oil tank30 and by adopting this structure, the lubricating oil (indicated with adotted arrow) traveling downward while rotating along the inner wallsurface of the oil separation chamber 33 can be guided into the oil tank30 with a high degree of efficiency. In addition, since this structureeliminates the need to form a special communicating hole to achievecommunication between the oil separation chamber 33 and the oil tank 30,the compressor can be provided as a compact unit and the work efficiencycan be improved as well.

The oil tank 30 is disposed so as to range from the rear head 3 throughthe valve plate 2 to the cylinder block 1, and the lubricating oilcollected in the oil tank 30 is guided into an axial passage 37 formedat the shaft 7 and extending along the axial direction via the bearinghousing chamber 11, is supplied from the axial passage 37 tolubrication-requiring portions around the shaft such as the thrustbearing 10, the peripheral surface of the shaft 7 against which thehinge ball 21 slides in contact and the shaft seal chamber 18 where themechanical seal is housed via radial passages 38, 39 and 40 formed so asto extend radially from the axial passage 37, and then is allowed toflow out into the crankcase 6. The axial passage 37 and the radialpassages 38 to 40 constitute a second lubricating oil supply paththrough which the lubricating oil is supplied from the oil tank 30 tothe lubrication-requiring portions around the shaft.

In the compressor, a continuous chamber 50 is formed so as to surroundthe individual cylinder bores 12 and the oil tank 30 in the cylinderblock 1 as illustrated in FIG. 2. The chamber 50, which is formed byleaving tubular walls 41 and 42 around the oil tank 30 and theindividual cylinder bores 12, is made to communicate with a suction port43 formed at the cylinder block 1 via a first passage 44 and is made tocommunicate with the suction chamber 26 at the rear head 3 via a secondpassage 45 formed at the valve plate 2. The first passage 44, thechamber 55 and the second passage 45 constitute a suction path throughwhich the working fluid is supplied so as to flow around the oil tank 30and the cylinder bores 12. In addition, the crankcase 6 and the chamber50 are made to communicate via a leak passage 46 formed as an orifice atthe cylinder block 1, and thus, the crankcase pressure is graduallyleaked into the chamber 50 (toward the suction chamber).

Furthermore, reinforcement ribs 47 are disposed at a height set byensuring that the ribs 47 do not block the suction passage to bridge theneighboring tubular walls 41 and 42 defining the oil tank 30 and thecylinder bores 12 and also to bridge the tubular walls 41 defining thecylinder bores 12 and the inner wall of the cylinder block 1.

In the structure described above, the working fluid taken in through thesuction port 43 flows into the chamber 50 via the first passage 44,passes around the cylinder bores 12 and the oil tank 30 to spread intothe entire chamber 50 and is guided into the suction chamber 26 via thesecond passage 45. The working fluid guided into the suction chamber 26is taken into the compression spaces 23 via the suction holes 24 duringthe descending stroke of the single-ended pistons 13, is compressedduring the ascending stroke and is then discharged into the dischargechamber 27 via the discharge holes 25.

When the discharge chamber 27 and the crankcase 6 come intocommunication with each other via the control passage 31, the workingfluid discharged into the discharge chamber 27, still containing thelubricating oil, is supplied to the peripheral edge of the swashplate20. In addition, since the top portion of the discharge chamber 27communicates with the oil separation chamber 33, the lubricating oilmixed in the working fluid becomes separated from the working fluid inthe oil separation chamber 33 and the separated lubricating oil iscollected into the oil tank 30. While the temperature of the lubricatingoil guided into the oil tank is high, the lubricating oil collected inthe oil tank is cooled down by the suction-side working fluid (thecoolant fed back through the low-pressure line in the freezing cycle thetemperature of which is relatively low) which flows through the chamber50 in the cylinder block 1, and thus, the lubricating oil is activelycooled to keep its viscosity at a high level. Furthermore, since thechamber 50 surrounds the cylinder bores 12 as well, the cylinder bores12 and the single-ended pistons 13 inserted at the cylinder bores, too,are cooled with the working fluid on the suction side.

The reinforcement ribs 47 disposed around the tubular walls 41 and 42defining the oil tank 30 and the cylinder bores 12 prevent deformationof the cylinder bores 12 that would otherwise occur due to thedescending load of the single-ended pistons 13 and thus, any structuralweakness resulting from the presence of the chamber 50 is corrected.Moreover, since the tightening bolts 5 are disposed further outwardrelative to the cylinder bores at positions with the same phase as thephase of the cylinder bores 12, the tightening bolts 5 are not insertedinside the chamber 50 and do not block the flow of the working fluid.

The structure described above includes two lubricating oil supply pathsystems, i.e., the lubricating oil supply path through which thelubricating oil is supplied to the peripheral edges of the swashplate 20via the control passage 31 and the lubricating oil supply path throughwhich the lubricating oil collected in the oil tank 30 is supplied tothe lubrication-requiring portions around the shaft via the passagesformed at the shaft 7. As a result, the lubricating oil can be suppliedto specific lubricating requiring portions in a desirable manner with ahigh degree of efficiency.

Namely, since the lubricating oil supplied to the sliding surfaces ofthe hinge ball 21 and the shaft 7 should be as pure as possible, themechanical seal 8 seals the space between the front head 4 and the shaft7 and the like, and the lubricating oil collected in the oil tank 30 issupplied directly to these portions, whereas the lubricating oil issprayed via the control passage 31 onto the peripheral edges of theswashplate 20 that slides in contact against the shoes 22, therebyassuring a reliable lubricating oil supply to the swashplate 20. In thismanner, the lubricating oil is supplied to the individuallubrication-requiring portions in a desirable manner.

It is to be noted that while the discharge chamber 27 is formed aroundthe oil tank 30 and the suction chamber 26 is formed around thedischarge chamber 27 in the structure described above, the positionalrelationship between the suction chamber 26 and the discharge chamber 27may be reversed. When the positions of the suction chamber and thedischarge chamber are reversed, the suction chamber 26 is formed so asto surround part of the oil tank 30 formed at the rear head 3 and, as aresult, it becomes possible to cool the oil tank 30 while the workingfluid flows inside the suction chamber 26 and in this case, the oil tank30 can be cooled even more effectively by cooling the oil tank 30 fromthe two sides, i.e., from the cylinder block side and the rear headside.

FIG. 5 presents an example of another structure that may be adopted inthe lubricating oil supply paths. While the first lubricating oil supplypath in this example assumes a structure similar to that shown in FIG.1, the second lubricating oil supply path is formed with a passagehaving one end thereof communicating with the oil tank 30 and anotherend thereof communicating with the shaft seal chamber 18 housing themechanical seal 8 via a housing passage 48 formed at the cylinder block1 and the front head 4, an axial passage 37 formed at the shaft 7 alongthe axial direction and radial passages 38, 39 and 40 extending from theaxial passage 37 along the radial direction to open atlubrication-requiring portions around the shaft such as the thrustbearing 10, the peripheral surface of the shaft 7 against which thehinge ball 21 slides in contact and the shaft seal chamber 18 housingthe mechanical seal 8. As a result, the lubricating oil having beencollected in the oil tank 30 is supplied to the shaft seal chamber 18via the housing passage 48 formed at the cylinder block 1 and the fronthead 4, is guided into the crankcase 6 via the radial bearing 16 and thethrust bearing 17 disposed between the thrust flange 15 and the fronthead 4 from the shaft seal chamber 18 and is also guided to the otherlubrication-requiring portions around the shaft from the radial passage40 at the shaft 7 via the axial passage 37 and the other radial passages38 and 39.

In addition, in this structural example, the bearing housing chamber 11and the chamber 50 at the cylinder block 1 are made to communicate witheach other via a leak passage 49 formed as an orifice at the cylinderblock 1 and the crankcase 6 and the chamber 50 are made to communicatewith each other via the thrust bearing 17 and the radial bearing 16disposed between the thrust flange 15 and the front head 4, the shaftseal chamber 18, the passages formed at the shaft 7 (the radial passage40 and the axial passage 37), the bearing housing chamber 11 and theleak passage 49 or via the thrust bearing 10 and the radial bearing 9disposed between the shaft 7 and the cylinder block 1, the bearinghousing chamber 11 and the leak passage 49. Thus, the crankcase pressureis ultimately leaked gradually into the chamber 50 (toward the suctionchamber) via the leak passage 49. It is to be noted that since the otherstructural features are identical to those in the previous structuralexample, the same reference numerals are assigned to the identicalfeatures to preclude the necessity for a further explanation.

In this structure, too, the lubricating oil separated at the oilseparation chamber 33 and collected into the oil tank 30 is cooled withthe suction side working fluid (the coolant with a relatively lowtemperature fed back through the low-pressure line in the freezingcycle) flowing through the chamber 50 at the cylinder block 1, and thelubricating oil thus cooled is supplied to the lubrication-requiringportions around the shaft. Through the two lubricating oil supply pathsystems, i.e., the lubricating oil supply path through which thelubricating oil is supplied to the peripheral edges of the swashplate 20via the control passage 31 and the path through which the lubricatingoil in the oil tank 30 is supplied to the lubrication-requiring portionsaround the shaft via the second lubricating oil supply path, thelubricating oil can be supplied in a desirable manner to the individuallubrication-requiring portions to achieve a high degree of efficiency inthe lubricating oil supply to the lubrication-requiring portions.

While the compressor described above adopts a structure achieved byfastening the front head 4, the cylinder block 1, the valve plate 2 andthe rear head 3 together by using the tightening bolts 5 disposed atpositions achieving the same phase as the individual cylinder bores 12,a more compact compressor with a sufficient level of pressurewithstanding performance and an airtight structure may be achieved bysymmetrically disposing two tightening bolts 51 with a smaller diameteraround each cylinder bore 12, instead of the tightening bolts 5 in theprevious example indicated with dotted lines, as shown in FIG. 6. Sincethe number of tightening bolts 51 used in this structure is greater thanthe number of cylinder bores 12, the front head 4, the cylinder block 1,the valve plate 2 and the rear head 3 can be fastened together moreevenly and more firmly. Furthermore, as the diameter of the tighteningbolts 51 is reduced compared to the diameter of the tightening bolts inthe related art, the overall diameter of the compressor itself can bereduced.

In a further application of the basic structure described above,sub-suction chambers 52 where the working fluid flowing in through thesuction port 43 is stored may be disposed between the suction port 43and the chamber 50, as shown in FIGS. 7 and 8.

Namely, in the structural example presented in FIG. 7, sub-suctionchambers 52 are formed by mounting a separate header 53 at the cylinderblock 1. The header 53 in FIG. 7 is mounted at the cylinder blockastride the area at which a tightening bolt 5 is inserted, a suctionport 43 and two sub-suction chambers 52 defined by a reinforcement rib54 communicating with the suction port 43 are disposed at the header 53and the sub-suction chambers 52 are each connected to the chamber 50 viaa first passage 44 formed to extend on either side of the area at whichthe tightening bolt 5 is inserted.

In the structural example presented in FIG. 8, a portion of theperipheral edge of the cylinder block 1 is made to distend so as tocover the area at which a tightening bolt 5 is inserted at the cylinderblock 1, two sub-suction chambers 52 defined by a reinforcement rib 54extending from the area at which the tightening bolt 5 is inserted and afirst passage 44 connecting each sub-suction chamber to the chamber 50through either side of the area at which the tightening bolt is insertedare formed at the distended portion and the suction port 43 formed atthe rear head is connected to the sub-suction chambers 52 via the valveplate 2. It is to be noted that in either of the structural examplesexplained above, a single sub-suction chamber 52 may be formed byomitting the reinforcement rib 54.

By adopting either of the structures described above, the working fluidflowing in via the suction port 43 is guided into the chamber 50 via thefirst passage 44 after traveling through the sub-suction chamber orchambers 52 and, as a result, the extent of suction pulsation can belowered.

It is to be noted that while the oil tank 30 is disposed near the centerof the cylinder block 1 in the examples explained above, the presentinvention is not limited to this positional arrangement and as long asthe oil tank can be cooled with the working fluid taken in through thesuction port 43, it may be disposed toward the peripheral edge of thecylinder block 1, as well. In addition, the suction port 43 and the oilseparation chamber 30, too, may be disposed at different positionsinstead of the positions assumed in the explanation given above.Furthermore, the structures described above may be adopted in clutchlesscompressors.

While an explanation is given above on an example in which thereciprocating compressor is a rotary swashplate compressor, the presentinvention may instead be adopted in an oscillating swashplatecompressor. While the front head 4, the cylinder block 1, the valveplate 2 and the rear head 3 are assembled together by using thetightening bolts 5 in the structure described above, a single ring nutmay be used instead of the tightening bolts 5, or they may be assembledtogether through welding or by using an adhesive, as well.

While the suction chamber 26 and the discharge chamber 27 are formed bylocking the rear head 3 onto the cylinder block 1 via the valve plate 2and the crankcase 6 is formed by locking the front head 4 onto thecylinder block 1 in the compressor in the explanation given above, thesuction chamber and the discharge chamber may instead be formed bylocking the front head to the cylinder block via the valve plate and thecrankcase may be formed by locking the rear head to the cylinder block.Any of the specific structural examples explained earlier may be adoptedin such a compressor.

Moreover, the specific structural features of the present invention maybe adopted in a compressor having the cylinder block and the second headprovided as an integrated unit or in a compressor having the valve platehoused within a groove formed at the cylinder block or the first head(having no tightening bolt holes).

INDUSTRIAL APPLICABILITY

As described above, according to the invention disclosed in claim 1, thelubricating oil separated at the oil separation means is collected inthe oil tank and the lubricating oil collected in the oil tank is cooledwith the working fluid taken in from the outside and guided into thesuction chamber. As a result, the viscosity of the lubricating oil canbe kept at a high level to achieve better lubrication.

According to the invention disclosed in claims 2 and 3, part of the oiltank is disposed at the cylinder block and the suction path is providedat the cylinder block so as to surround the oil tank. Thus, the workingfluid guided into the suction chamber, which is allowed to flow aroundthe oil tank while flowing through the suction path at the cylinderblock, cools the oil tank with a high degree of efficiency.

According to the invention disclosed in claim 4, part of the oil tank isdisposed at the first head and the suction chamber is formed at thefirst head so as to surround the oil tank. Thus, the working fluidflowing through the suction chamber cools the oil tank.

According to the invention disclosed in claim 5, the oil separationmeans achieves centrifugal separation, the oil separation chambercommunicating with the discharge chamber is formed so as to partiallyoverlap with the oil tank and is thus made to communicate with the oiltank, and the lubricating oil having become separated at the oilseparation means is guided into the oil tank. Consequently, thelubricating oil can be collected into the oil tank with a high degree ofefficiency. In addition, it is not necessary to form a specialcommunicating hole that would be otherwise needed to guide the separatedlubricating oil into the oil tank.

According to the invention disclosed in claim 6, a chamber is formed soas to surround the cylinder bores as well and, as a result, the cylinderbores and the pistons inserted therein, too, can be cooled with a highdegree of efficiency.

According to the invention disclosed in claim 7, reinforcement ribs aredisposed to bridge tubular walls with each other in the structure inwhich the tubular walls are left so as to define a chamber around theoil tank and the cylinder bores, and thus, deformation of the cylinderbores that would otherwise be induced by the descending load of thepistons can be prevented.

According to the invention disclosed in claims 8 and 9, two lubricatingoil path systems are formed to make it possible to supply thelubricating oil in a desirable manner to the specific individuallubrication-requiring portions.

According to the invention disclosed in claim 10, the tightening boltsused to fasten together the cylinder block, the valve plate, the firsthead and the second head are disposed further outward relative to thecylinder bores at positions achieving the same phase as the phase of thecylinder bores, and thus no obstacle is present in the suction path.

According to the invention disclosed in claim 11, a greater number oftightening bolts compared to the number of cylinder bores is used tofasten together the cylinder block, the valve plate, the first head andthe second head. Consequently, the compressor can be provided as acompact unit achieving a high level of pressure withstanding performanceand a highly airtight structure. According to the invention disclosed inclaim 12, sub-suction chambers where the working fluid flowing inthrough the suction ports is stored are disposed between the suctionport and the chamber so as to lower the extent of the suction pulsation.

1. A reciprocating compressor comprising: a cylinder block having formedtherein a plurality of cylinder bores; a valve plate having formedtherein pairs of holes with each pair constituted of a suction hole anda discharge hole, in correspondence with one of said cylinder bores; afirst head fixed to said cylinder block via said valve plate and havingformed therein a suction chamber that is allowed to come intocommunication with said suction hole and a discharge chamber that isallowed to come into communication with said discharge hole; a secondhead fixed to said cylinder block having formed therein a crankcase; ashaft rotatably disposed so as to pass through said crankcase; andpistons that reciprocally slide inside said cylinder bores as said shaftrotates, characterized in: that an oil separation means that separateslubricating oil mixed in a working fluid discharged into said dischargechamber and an oil tank in which the lubricating oil having beenseparated at said oil separation means is stored are provided; and thatthe lubricating oil stored in said oil tank is cooled with a workingfluid taken in from outside and guided into said suction chamber.
 2. Areciprocating compressor according to claim 1, characterized in: thatpart of said oil tank is disposed at said cylinder block; and that asuction path through which the working fluid flows is disposed so as tosurround said oil tank at said cylinder block.
 3. A reciprocatingcompressor according to claim 2, characterized in: that said suctionpath is constituted with a suction port through which the working fluidis taken in from outside, a chamber formed at said cylinder block so asto surround said oil tank and to open toward said valve plate, a firstpassage communicating between said suction port and said chamber and asecond passage formed at said valve plate and communicating between saidchamber and said suction chamber.
 4. A reciprocating compressoraccording to claim 1, characterized in: that part of said oil tank isdisposed at said first head; and that said suction chamber is formed atsaid first head so as to surround said oil tank.
 5. A reciprocatingcompressor according to claim 1, characterized in: said oil separationmeans includes an oil separation chamber communicating with saiddischarge chamber and achieves centrifugal separation whereby theworking fluid having flowed in from said discharge chamber is rotated insaid oil separation chamber to separate the lubricating oil, with partof said oil separation chamber made to overlap with said oil tank toachieve communication.
 6. A reciprocating compressor according to claim3, characterized in: that said chamber is formed so as to surround saidcylinder bores as well.
 7. A reciprocating compressor according to claim6, characterized in: that said chamber is formed by leaving tubularwalls around said oil tank and around said cylinder bores; and thatreinforcement ribs bridge said tubular walls with each other.
 8. Areciprocating compressor according to claim 3, characterized in: that acontrol passage, the degree of openness of which is adjusted with apressure control valve is formed between said discharge chamber and saidcrankcase; that a first lubricating oil supply path formed by opening anend of said control passage facing said crankcase toward a peripheraledge of said swash plate and a second lubricating oil supply paththrough which the lubricating oil collected in said oil tank is suppliedto lubrication-requiring portions around said shaft via a passage formedat said shaft are achieved; and that said crankcase and said chamber aremade to communicate with each other via a leak passage formed at saidcylinder block.
 9. A reciprocating compressor according to claim 3,characterized in: that a control passage, the degree of openness ofwhich is adjusted with a pressure control valve is formed between saiddischarge chamber and said crankcase; that a first lubricating oilsupply path formed by opening an end of said control passage facing saidcrankcase toward a peripheral edge of said swash plate and a secondlubricating oil supply path through which the lubricating oil collectedin said oil tank is supplied to lubrication-requiring portions aroundsaid shaft via a passage formed at said cylinder block and said secondhead and also via a passage formed at said shaft communicating with saidpassage are achieved; and that said crankcase and said chamber are madeto communicate with each other via said passage formed at said shaft anda leak passage formed at said cylinder block and communicating with saidpassage.
 10. A reciprocating compressor according to claim 1,characterized in: that said cylinder block, said valve plate, said firsthead and said second head are fastened together with tightening bolts;and that said tightening bolts are disposed further outward relative tosaid cylinder bores at positions with a phase matching the phase of saidcylinder bores.
 11. A reciprocating compressor according to claim 1,characterized in: that said cylinder block, said valve plate, said firsthead and said second head are fastened together with tightening bolts;and a greater number of tightening bolts compared to the number ofcylinder bores are used.
 12. A reciprocating compressor according toclaim 3, characterized in: that a sub-suction chamber in which theworking fluid flowing in through said suction port is stored is disposedbetween said suction port and said chamber.